# Proper Motions of Jets on the Kiloparsec Scale: New Results with HST

## TL;DR

This study uses 20-year HST observations to measure the proper motions of kiloparsec-scale optical jets, revealing velocity profiles and deceleration patterns from near the black hole outward.

## Contribution

First to measure proper motions of kiloparsec-scale optical jets with high precision, linking parsec and kiloparsec scale velocities for a comprehensive jet profile.

## Key findings

- Jets in FR I galaxies accelerate up to 100 pc from the core.
- Proper motions indicate jet deceleration beyond 100 pc.
- Velocity profiles connect near the black hole to large-scale jet behavior.

## Abstract

The Hubble Space Telescope recently celebrated 25 years of operation. Some of the first images of extragalactic optical jets were taken by HST in the mid-1990s; with time baselines on the order of 20 years and state-of-the-art astrometry techniques, we are now able to reach accuracies in proper-motion measurements on the order of a tenth of a milliarcsecond per year. We present the results of a recent HST program to measure the kiloparsec-scale proper motions of eleven nearby optical jets with Hubble, the first sample of its kind. When paired with VLBI proper-motion measurements on the parsec scale, we are now able to map the full velocity profile of these jets from near the black hole to the final deceleration as they extend out into and beyond the host galaxy. We see convincing evidence that weak-flavor jets (i.e., FR Is) have a slowly increasing jet speed up to 100 pc from the core, where superluminal components are first seen.